Fix: #2141: Skip Back issue when skipping from watch

[bjtitus]

Fixes #2141

In #2041 we added logic to ignore skips which would skip ahead. However, the Watch skipBack function is called on a background thread and the timer never appears to fire, causing previousSeekTime to never be reset to nil, breaking all future skip backs.

Considerations

I also considered adding the Debouncer to the Main RunLoop instead of scheduling on its current RunLoop. This would apply to other caller of skipBack but I checked all of these and I believe all will come from the main thread. I'm concerned this could cause race conditions if the callback relies on the original behavior.

To test

• Play an episode on the phone
• Use the watch app to skip back
• Check that skip back worked
• Try skipping back on the phone
• Ensure that skipping worked

Checklist

• I have considered if this change warrants user-facing release notes and have added them to CHANGELOG.md if necessary.
• I have considered adding unit tests for my changes.
• I have updated (or requested that someone edit) the spreadsheet to reflect any new or changed analytics.

[dangermattic]

	1 Warning
⚠️	This PR is assigned to the milestone 7.73 ❄️. The due date for this milestone has already passed. Please assign it to a milestone with a later deadline or check whether the release for this milestone has already been finished.

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[SergioEstevao]

Tested this on device and it's working great!